Fabric for a machine for producing a fiber web

ABSTRACT

A fabric for a machine that produces a fiber web, especially a paper-, board-, tissue- or pulp web. The fabric has a flat woven base material having a top side and a bottom side, two terminal ends separated in a machine direction. Folds are formed in the flat woven base material separated in the machine direction, whereby the two terminal ends are located under the bottom side surface. The two terminal ends are arranged adjacent to each other or they overlap each other. Seam loops are located at the folds. The novel fabric has at least one woven component, that is a multi-layer weave, especially a two-layer weave.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a fabric for a machine that produces a fiber web, especially a paper-, board-, tissue- or pulp web. The fabric is formed of a flat woven base material having a top side and a bottom side, two terminal ends separated in a machine direction, folds formed in the flat woven base material being separated in the machine direction. The two terminal ends are located under the bottom side surface, and the two terminal ends are arranged adjacent to each other or overlap each other, and seam loops are located at the folds.

In modern paper machines, the paper web is transported on different kinds of paper machine clothings such as wires or felts through the process. In the press section of a paper machine, press felts are widely used, that comprise one or more fibrous batt layers and a base structure made from woven material.

From a user's perspective, in many applications, the void volume through the lifetime of the fabric is a critical requirement for good performance. Of special interest are seamable press felts, since they are easier to handle. Many of these applications, that require a substantial void volume for good performance—for example in board and packaging paper machines—are also sensitive to seam marks and therefore also require a seam with uniform dewatering and good structural integrity for full life performance. A base fabric design is required which provides both necessary void volume and seam design to ensure a uniform pressure profile and dewatering through life.

From an economic perspective, the fabric should be quick and easy to produce. Therefore, it is known, for example from commonly assigned U.S. Pat. No. 8,043,477 B2 and its counterpart WO 2009/106182 to use a simple, flat woven material and to fold it in order to produce a two ply base structure with seam loops for a seamable fabric. The use of a flat woven material is advantageous, since it can easily be produced on a comparably simple and cheap loom and the production time is much faster compared to an endlessly woven structure. The task of preparing a seam for such fabrics is also discussed in the literature. See, for instance, commonly assigned U.S. Pat. No. 8,353,252 B1 and its counterpart WO 2013/083468.

Unfortunately, in some important applications, the two ply designs as described in U.S. Pat. No. 8,043,477 B2 and WO 2009/106182 or in U.S. Pat. No. 8,353,252 B1 and 2013/083468 do not provide enough void volume to guarantee sufficient dewatering properties.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a fabric for a web producing machine which overcomes the above-mentioned and other disadvantages of the heretofore-known devices and methods of this general type and of the present invention and which provides for a fabric for a machine to produce a fiber web, especially a paper-, board-, tissue- or pulp web, where—or pulp web, where the base structure can be easily and economically produced while providing sufficient void volume for demanding applications.

With the foregoing and other objects in view there is provided, in accordance with the invention, a fabric for a machine for producing a fiber web, the fabric comprising:

-   -   a flat woven base material having a top side and a bottom side,         two terminal ends separated from one another in a machine         direction;     -   folds formed in the flat woven base material, said folds being         separated in the machine direction and said two terminal ends         being located under the bottom side surface;     -   said two terminal ends being arranged adjacent one another or         overlapping one another and said folds having seam loops located         at said folds; and     -   the novel fabric has at least one woven component formed as a         multi-layer weave, preferably a two-layer weave.

In other words, the invention provides for a fabric for a machine that produces a fiber web, especially a paper-, board-, tissue- or pulp web. The fabric comprises a flat woven base material having a top side and a bottom side, two terminal ends separated in a machine direction, folds formed in the flat woven material being separated in the machine direction whereby the two terminal ends are located under the bottom side surface. The two terminal ends may one of be arranged adjacent to each other or overlapping each other. The seam loops are located at the folds.

Pursuant to the invention, the fabric comprises at least one woven component that is a multi-layer weave, especially a two-layer weave.

It must be noted, that some multi-layer weaves, especially two layer weaves can be easily and quickly produced on the same economical looms, as the flat woven material known from the state of the art.

In a preferred implementation of the present invention, the flat woven base material is a multi-layer weave, especially a two-layer weave. This flat woven base can then be produced on the same looms, as the classical one layer flat woven base with only minor adaption's to the loom settings. In the case of a two-layer weave, the resulting fabric has approximately twice the void volume, compared to the classical. But the production cost and production time is similar to the classical design. In addition, also no major changes in the processing process are necessary.

In a further preferred embodiment of the invention the fabric further comprises an insert located between the folds, the bottom side surface and the terminal ends arranged adjacent to each other.

This insert can be designed to further increase the void volume of the fabric. Depending on the desired properties, the fabric may comprise a single insert or two or more inserts. In the case of several inserts, one may choose to use the same inserts or different types of inserts.

Several materials and designs may be used as an insert. The insert may for example be a membrane, flexible foam, a nonwoven structure like a batt layer or a foil-like structure to name just a few. By using an elastomeric material like e.g. Polyurethane in the insert, it is possible to enhance further fabric properties. The elastomeric material in the insert may for example be in the form of a sheet-like structure comprising a polyurethane.

In a particularly favorable embodiment of the invention, at least one insert is a woven insert. With a woven insert, many favorable implementations of the invention are possible. In one implementation, the insert can be a multi-ply, especially a two ply weave. This multi-ply insert could be combined with a flat woven base material that is only a one ply weave.

Alternatively, the insert and the flat woven base material can be made from the very same material of two-ply or multi-ply weave. This is a very favorable embodiment of the invention, since for the production of the fabric one has to provide only one kind of weave on a large reel.

In one favorable embodiment the two terminal ends one of are arranged adjacent to each other or overlap each other in a region offset from the center between the folds. In an especially favorable embodiment, this region is located less than 1.2 m (˜4 ft.) from one of the folds, or even between 0.9 m (˜3 ft.) and 2.5 cm (˜1 inch) from one of the folds. This arrangement can facilitate the further processing of the fabric, for example, if the terminal ends are sewn to the bottom side surface.

For the use in a press section of a paper machine, the fabric may be implemented as a felt. Therefore it is favorable, that the fabric further comprises at least one layer of fibrous batt. In many applications, there will be more than one layer of batt.

Advantageously the fabric may be a seamable fabric, comprising only a single seam.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a fabric for a fiber web-producing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A, 1B and 1C are schematic views of portions of a fabric according to the present invention;

FIG. 2 is a schematic view of a fabric according to the invention; and

FIGS. 3A and 3B show parts of a fabric according to alternative embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first, particularly, to FIGS. 1A 1B, 1C and FIG. 2, there is shown a flat woven base 1 with a top side 2 and a bottom side 3. The base fabric is woven from MD (machine direction) yarns 6 and CD (cross direction) yarns 7, 7 a. The flat woven base 1 of FIG. 1 (1A, 1B, 1C) is formed as a multi-layer weave, especially a two-layer weave.

According to the invention, the flat woven base 1 is folded and terminal ends 4 of the flat woven base 1 are located under the bottom side 3. By doing so, two folds 5 are created. At these folds 5, seam loops 8 are created which can be used to create a seamable fabric. In the exemplary structure shown in FIGS. 1B, 1C and 2, the seam loops are created by removing some CD yarns 7 a in the region of the folds 5. Additionally, as shown in FIG. 1C, there may be one or more stitchings to enhance the seam loops, but these stitchings might as well be omitted. There are, according to the invention, several other possibilities for form seam loops at the folds.

FIG. 2 shows a schematic overview of a flat woven base layer 1 folded according to the invention. The two terminal ends 4 of the flat woven base layer 1 are arranged adjacent to each other. The two terminal ends 4 could also overlap each other a little bit. To facilitate the production of the fabric, it can be beneficial to place the terminal ends 4 in a region offset from the center between the folds 5. This placement is especially helpful, if the terminal ends are fixed, e.g. sewn to the bottom side 3 of the flat woven base 1.

By having a flat woven base 1, that is a multi-layer weave—here: a two-layer weave—as in FIG. 2, the folding process easily creates a base structure for a fabric, e.g. a press fabric that has four woven layers and thereby providing a significant amount of void volume in the fabric. The structure shown in FIG. 2 may for example be embellished with one or more layers of fibrous batt on one side or on both sides.

FIGS. 3A and 3B show embodiments of the present invention, where the fabric further comprises an insert 10, 10 a located between the folds 5. In FIG. 3A, the flat woven base weave 1 is a multi-layer weave. This insert 10 can be designed to further increase the void volume of the fabric. Depending on the desired properties, the fabric may comprise a single insert 10 or two or more inserts 10. In the case of several inserts 10, one may choose to use the same inserts 10 or different types of inserts 10.

Several materials and designs may be used as an insert 10. The insert 10 may for example be a membrane, flexible foam, a nonwoven structure like a batt layer or a foil-like structure to name just a few. By using an elastomeric material like e.g. Polyurethane in the insert 10, it is possible to enhance further fabric properties.

FIG. 3B shows a different embodiment of the present invention. Here, the insert 10 a is a woven component that is a multi-layer, especially a two layer woven component. The flat woven base 1 in this embodiment may be any kind of woven structure, either a multi-layer or a single layer weave. 

1. A fabric for a machine for producing a fiber web, the fabric comprising: a flat woven base material having a top side and a bottom side, two terminal ends separated from one another in a machine direction; folds formed in the flat woven base material, said folds being separated in the machine direction and said two terminal ends being located under the bottom side surface; said two terminal ends being arranged adjacent one another or overlapping one another and said folds having seam loops located at said folds; and at least one woven component formed as a multi-layer weave.
 2. The fabric according to claim 1, wherein said multi-layer weave is a two-layer weave.
 3. The fabric according to claim 1, wherein the machine is configured to produce a paper web, a board web, a tissue web or pulp web.
 4. The fabric according to claim 1, wherein said flat woven base material is a multi-layer weave.
 5. The fabric according to claim 4, wherein said flat woven base material is a two-layer weave.
 6. The fabric according to claim 1, which further comprises an insert located between said folds, said bottom side surface and said terminal ends arranged adjacent to one another.
 7. The fabric according to claim 6, wherein said at least one insert is a woven insert.
 8. The fabric according to claim 6, wherein said at least one woven insert is a multi-layer weave.
 9. The fabric according to claim 8, wherein said at least one woven insert is a two-layer weave.
 10. The fabric according to claim 1, wherein said two terminal ends are arranged adjacent one another or overlap one another in a region that is offset from a center between said folds.
 11. The fabric according to claim 1, wherein one or more cross direction yarns are removed from said flat woven base material at one of said folds or at both of said folds in order to form said seam loops.
 12. The fabric according to claim 1, which further comprises at least one layer of fibrous batt.
 13. The fabric according to claim 1, formed as a seamable fabric comprising only a single seam. 